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AQA A-Level Physics > Particles 1 > Flashcards

Particles 1 Flashcards

1
Q

How big is a nucleus?

A

approx diameter: 10^-14m/10^-15m

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2
Q

How big is an atom?

A

approx diameter: 10^-10m

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3
Q

Define a nucleon

A

A constituent particle of a nucleus: a proton or neutron

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4
Q

Define a nuclide

A

A specific isotope of a nucleus

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5
Q

Give an example of a nuclide

A

C-14 and C-12 are isotopes of carbon but they are different nuclides

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6
Q

Define an isotope

A

a nucleus with the same number of protons but a differing number of neutrons

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7
Q

What is meant by specific charge?

A

the charge per unit mass

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8
Q

How do you calculate specific charge?

A

specific charge = (net charge) / (total mass)

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9
Q

What is an ion?

A

a charged atom

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10
Q

a Ca
b
has how many protons, neutrons and electrons?

A

protons: b
neutrons: a - b
electrons: b

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11
Q

What is the nucleon number?

A

the number of protons and neutrons in the atom

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12
Q

At less than ____ the strong nuclear force is ______

A

0.5 fm

repulsive

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13
Q

Between ____ and ____ the strong nuclear force is _______

A

0.5 fm
3.0 fm
attractive

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14
Q

Beyond ____ the strong nuclear force is ____

A

3.0 fm

zero

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15
Q

(In the nucleus) The electromagnetic force just acts between the ______ and is therefore ______

A

protons

repulsive

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16
Q

The electromagnetic force is much ______ than the strong nuclear force

A

weaker

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17
Q

The strong nuclear force acts between all of the _____ and has nothing to do with _____

A

nucleons

charge

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18
Q

What is an alpha particle?

A

a helium nucleus

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19
Q

What is the mass number?

A

the number of protons + the number of neutrons

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20
Q

What is the atomic number?

A

the number of protons

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21
Q

What is the atomic and mass number of an alpha particle?

A

mass number - 4

atomic number - 2

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22
Q

What is an alpha particle in terms of the energy it holds?

A

mono-energetic

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23
Q

What is a beta particle?

A

an electron

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24
Q

What is a beta particle in terms of the energy it holds?

A

has a range on energies

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25
Q

What did the fact that an electron has a range of energies lead to the discovery of?

A

an antineutrino

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26
Q

What does an antineutrino do in beta decay?

A

shares the energy with the beta particle

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27
Q

Give three properties of a neutrino

A

1) neutral
2) very small mass (possibly mass-less)
3) therefore interacts very weakly
(shares energy with electron in beta decay)

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28
Q

Define a photon

A

a discrete amount of energy that forms EM radiation with both particle and wave properties

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29
Q

What is the electromagnetic spectrum in order of ascending frequency?

A

1) radio
2) micro
3) infrared
4) visible light
5) ultra-violet
6) x-ray
7) gamma

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30
Q

Define 1 electrovolt

A

the energy an electron gains when it moves through a potential difference of 1V

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31
Q

What is 1 eV equal to in Joules?

A

1 eV = 1.6 x 10^-19 J

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32
Q

What is rest energy?

A

Energy due to mass

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33
Q

Describe pair production by a photon

A

1) a photon collides with a nucleus (the nucleus so that momentum is conserved)
2) if the photon has sufficient energy, a particle and an antiparticle are formed

34
Q

What is the minimum energy of the photon equal to in pair production?

A

Emin = hf min = 2Eo

35
Q

Why is the minimum energy needed in pair production equal to 2Eo?

A
  • charge has to be conserved during the collision

- so two particles need to be made (a particle and an antiparticle)

36
Q

Explain why there is a minimum energy required in pair production by a photon

A

1) energy of the photon needs to provide at least the rest masses
2) this is the energy needed to produce both a particle and an antiparticle of velocity 0
3) as the particle and the antiparticle have rest energies

37
Q

What equation shows the energy in pair production by a photon?

A

hf = 2Eo + KE

38
Q

If a photon of a higher energy is used in pair production, compared to a photon of lower energy, what are the two possible differences in the particles produced?

A

1) could make more particles

2) could make the same number of particles but with more KE

39
Q

When does annihilation occur?

A

When a particle meets its antiparticle

40
Q

Define annihilation

A

the process by which a particle and its antiparticle meet and their mass gets converted into energy in the form of a pair of photons

41
Q

Why are two photons produced in annihilation?

A

To conserve momentum

42
Q

What equation shows the energy in annihilation?

A

2Eo (+ KE) = 2hf

43
Q

Define a quark

A

a fundamental particle that makes up hadrons

44
Q

Define a hadron

A

a composite subatomic particle made of two or more quarks held together by the strong nuclear force

45
Q

Give an example of a hadron

A

proton

neutron

46
Q

Define a baryon

A

a type of composite subatomic particle which contains three quarks (belong to the hadron family of particles)

47
Q

Define a meson

A

hadronic subatomic particle composed of a quark-antiquark pair

48
Q

Give an example of a meson

A
  • pion

- kaon

49
Q

Define a lepton

A

a fundamental particle that does not interact via the strong nuclear force
(feels the weak force but not the strong force)

50
Q

Give 4 examples of a lepton

A

1) electron
2) electron neutrino
3) muon
4) muon neutrino

51
Q

What is the only stable free baryon?

A

the proton

52
Q

What are cosmic rays?

A

very high energy particles from space

53
Q

The existence of the neutrino was hypothesised to account for…

A

conservation of energy in beta decay

54
Q

What are the two classes of hadrons?

A

1) baryons

2) mesons

55
Q

What do all baryons eventually decay to?

A

a proton

56
Q

What does a muon decay into?

A

an electron

57
Q

Define a pion

A

a type of meson that contains no strange quarks, it is the exchange particle of the strong nuclear force

58
Q

Define a kaon

A

a type of meson which consists of one up or down quark and one strange quark, they decay into pions

59
Q

What do kaons decay into?

A

pions

60
Q

What is a boson?

A

a force carrying particle

61
Q

Define fundamental particles

A

particles that are indivisible

62
Q

The electromagnetic force affects all particle categories if they…

A

are charged

63
Q

What must be conserved in all interactions?

A
  • energy
  • momentum
  • charge
  • baryon number
  • lepton electron number
  • lepton muon number
64
Q

Weak interactions cause quarks to…

A

decay (change flavour)

65
Q

Strong interactions cause _____________ of quarks

A

pair production

66
Q

Strangeness gives particles…

A

unusually long lifetimes

67
Q

In what interactions are strange particles produced?

A

in strong interactions

68
Q

In what interactions are strange particles conserved?

A

in strong interactions

69
Q

Through what interactions do strange particles decay?

A

through weak interactions

70
Q

In what interactions is strangeness not always conserved?

A

in weak interactions

71
Q

What is the range of the electromagnetic force?

A

Infinite

72
Q

What is the carrier particle for the electromagnetic force?

A

(virtual) photons

73
Q

How strong in the weak nuclear force compared to the electromagnetic force?

A

10^-11 times EM

74
Q

What is the carrier particles for the weak nuclear force?

A
  • W+
  • W-
  • (or Zo)
75
Q

How strong in the strong nuclear force compared to the electromagnetic force?

A

100 times greater than EM

76
Q

What are the carrier particles of the strong nuclear force?

A

Gluons (intranucleon)

Pions (internucleon)

77
Q

Define electron capture

A
  • When a proton in the nucleus captures an electron from the inner orbital
  • It generates a neutron and a neutrino
78
Q

What must be seen on all Feynman diagrams?

A
  • all conservation laws apply at each junction
  • paths diagonally to show movement through time
  • bosons shown with a wiggly line
79
Q

What are the axis of a Feynman diagram?

A

y-axis: time

x-axis: space

80
Q

Give 4 roles of exchange/carrier particles

A
  • transfer momentum
  • transfer energy
  • transfer force
  • (sometimes) transfer charge
81
Q

What is meant by an exchange/carrier particle?

A
  • moves between one object/particle and another
  • gives rise to the force between the particles
  • transfer force, energy, momentum and sometimes charge

AQA A-Level Physics (21 decks)

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